This invention concerns detergent compositions, their manufacture, their use as additives for gasolines and the resultant improved gasoline compositions which possess good anti-rust and detergent properties as concerns the carburator and the admission systems. These detergent compositions are characterized by the fact they are obtained by reacting a specific polyamine with a complex mixture resulting from the partial condensation of an unsaturated anhydride with an olefin.
Irregular idling and motor stalling have long been known as problems associated with the running of motor cars operated with carburators.
A reason why irregular idling and stalling occur is the accumulation of deposits on the throttle valve of the carburator and on the surrounding walls. This accumulation of deposits disturbs the normal flow of air through the carburator, thus leading to rich fuel mixtures. The deposits can result, for example, from the accumulation of impurities or dust from the air or from the recycling of crank-case gas.
On the other hand, these too rich fuel mixtures do not burn completely, so that the air pollution increases with the content of partially unburnt fuel particles.
Modern carburators of high capacity have a complex structure. Even though few deposits and residues are present, their presence in the fine control parts of these carburators greatly disturbs the operation thereof, thus resulting in an unsatisfactory composition of the fuel/air mixture so that the CO/CO.sub.2 ratio increases.
This can be remedied either by an expensive periodical cleaning of the carburator and the heads of the admission valves, or by increasing the normal idling speed, which results in a greater difficulty for driving the vehicle and an unnecessary increase of the fuel consumption.
It is known that the deposits in the carburator can be reduced or the accumulation of these deposits can be inhibited by using fuels containing additives called detergents for carburators.
In addition to the detergent additives for carburators, the modern fuels necessitate other additives to improve the behaviour of the fuel, for example those which provide for an anti-rust protection and a limitation of the deposits in the admission system. The additives are preferably multi-functional additives.
Although a number of multi-functional additives have been proposed in the art, many of them are not acceptable, either since they have undesirable effects or must be used in excessive amounts, to obtain the desired properties.
U.S. Pat. No. 3,920,698 discloses nitrogen compounds having excellent detergent, anti-corrosion and anti-frost effects. However the products mentioned in this patent do not fully eliminate the deposits formed on the hot surfaces of the admission circuit.